Bone marrow amyloid in patients with M-component.

Amyloid substance was looked for in bone marrow aspirates of 28 patients presenting an M-component, in association with different illnesses (plasmocytoma, chronic lymphatic leukemia, lymphocytic lymphoma, "benign monoclonal gammapathy" and liver cirrhosis). Amyloid was detected in 12 out of 20 patients with plasmocytoma (60%) and in 3 out of 8 patients with other illnesses (37.5%); it was found in 9 out of 13 cases (69.2%) presenting exclusive light chain production and in 6 out of 15 cases (40%) with a monoclonal complete Ig. Lambda type light chain, either free or Ig-bound, was slightly more often (6 cases out of 10, 60%) associated with amyloidosis than was K (9 cases out of 17, 52.9%). Bone marrow appeared to be more frequently involved than other sites considered elective such as rectal mucosa. Amyloid appeared as an intensively fluorescent substance present intercellularly in areas of variable number and size.